It has heretofore been proposed to integrate the operation of numerically controlled machine tools into a computer network. The typical reason for construction of such machine tool computer networks is the simplified access to and maintenance of the machine tool part programs for the numerically controlled machine tools. At one time it was standard to provide the machine tool part programs for numerically controlled machine tools via a punched paper tape. This punched paper tape was loaded into a reader at the particular machine tool and read one program step at a time during the operation of the machine tool. Such a paper tape system was cumbersome for several reasons. First, such a system required physical relocation of the paper tape within the reader in order to rerun the program for an additional part, or to rerun one block (step) of the program such as, for example, to repeat a particular single operation of the machine tool. These punched paper tapes generally are too easily damaged to have a reasonable lifetime on the shop floor. Lastly, it is difficult to insure that each machine tool is using the latest and best version of the machine tool part program for a particular operation when numerous differing paper tape programs are available on the shop floor. Thus it is difficult to control the machine tool operation using paper tapes.
A computer network for providing machine tool part programs for numerically controlled machine tools solves many of these problems. In such a computer network, the machine tool operator would obtain the machine tool part program for the machine tool from the computer network. This machine tool part program would be stored in a permanent magnetic disk medium at a central location. This ensures availability of the machine tool part program. In addition, each machine tool doing the same operation would be supplied with the same machine tool part program. This means it is very easy to distribute to all the machine tools the latest and best version of a particular machine tool part program for a particular part.
U.S. Pat. No. 3,668,653 issued to Fair et al on Jun. 6, 1972 entitled "Control System" discloses an example of such a computer network for numerically controlled machine tools. The control system of the Fair et al patent includes an additional feature. The program recalled from the computer network can be operated in a RUN mode or in a CONVERSATION mode. In the RUN mode the individual machine tool operator has only limited capability of modifying the machine operation. This limited capability involves such things as withdrawal of the tool to correct tool breaks and the skipping or repeating of individual blocks of the machine tool part program such as employed when reworking a previously worked part. The CONVERSATION mode permits more extensive modification and editing of the machine tool part program specifically in "source language". This CONVERSATION mode permits a master machine tool operator or programming engineer to create, modify or debug a machine tool part program for a particular part. After modification this machine tool part program can be used by this or other machine tools in the RUN mode to produce parts.
A further example of a computer network employed with machine tools is U.S. Pat. No. 4,251,848 issued Feb. 17, 1981 to Cambigue et al entitled "Paging, Status Monitoring and Report Compiling System for Support, Maintenance and Management of Operator-Supervised Automatic Industrial Machines." The Cambigue patent teaches a distributed microcomputer network for communication of machine tool operator Initiated CALL and encoded STATUS signals. Each machine tool includes an operator console that is connected to the distributed microcomputer network. This system permits the machine tool operator to initiate a CALL that is automatically transmitted to maintenance personnel via either a terminal or a printer connected to the microcomputer network, and is Indicated on a visual display board. Thus the machine tool operator need not leave his work station to report problems to the proper support personnel. This system includes a set of thumb wheel switches for the machine tool operator to enter the proper CALL and STATUS signals. In addition, the system automatically detects the ON and OFF status of the machine tool and the ON and OFF status of the operator feed rate override. The network logs and reports any change in the ON and OFF status of the machine tool or of the operator feed rate override. The Cambigue patent teaches that the use of a distributed network of microcomputers for the communication system is advantageous because the communication system is not dependent on the availability of any particular computer.
The Applicant believes that the prior art does not provide the tools necessary to manage the operation of a plurality of numerically controlled machine tools to the best advantage. Greater feedback of events occurring at the numerically controlled machine tools, beyond that used in the closed loop servo system and beyond knowing that the machine tool is running or not, is needed. It is axiomatic that it is impossible to determine how to do something better if you don't know how you are doing it now. Greater feedback provides additional information to industrial/manufacturing engineers permitting them to make substantiated decisions for improving the processes occurring at the machine tools. As a result, the industrial/manufacturing engineers can further optimize the utilization of the numerically controlled machine tools.